Production of shaped objects from viscose



Patented June 14, 1960 2,940,818 PRODUCTION OF SHAPED OBJECTS FROM VISCQSE V Egidius Walters, Heinsberg, Rhineland, Germany, as-

signor to American Enka Corporation, Enka, N.C., a corporation of Delaware No Drawing. Filed Oct. 25, 1955, Ser. No. 542,766 Claims priority, application Germany Nov. 25, 1954 1 Claim. (Cl. 1854) This invention relates to a process for the production from viscose of artificial threads and other shaped objects, including films, having greatly improved properties as regards their resilience and their smaller degree of swelling. The invention also relates to the resulting products.

One of the principal objects of the present invention is to provide a new and improved method for spinning artificial products such as threads and other shaped objects from viscose in such manner as to confer upon them greatly improved properties as regards their strength and elasticity. A further object of the invention is to provide a new and improved method for producing products of the kind just indicated having unusually strong and well-defined peripheral zones. A still further object of the invention is to provide improved products of the kind indicated.

The manner in which these and other objects and features of the invention are attained will appear more fully from the following description thereof, in which reference is made to typical and preferred procedures in order to indicate more fully the nature of the invention, but with out intending to limit the invention thereby.

The attention of rayon manufacturers has for a long time been directed to the production of threads having improved strength and elongation properties. strength values with elongations having a high elasticity factor may generally be found with threads which comprise a strongly formed and defined peripheral zone. It is possible to obtain such threads by spinning unripe viscoses in baths containing zinc sulphate and having a low acid content. It was assumed that the Zinc sulphate content of the bath was an essential condition for the formation of the strong peripheral zone. Moreover, processes have become known by which it is possible still further to improve the textile data, without it being necessary to work with disproportionately large amounts of zinc sulphate. The addition of monoamines to the viscose or to the spinning bath has proved successful in this respect. A condition is, however, that the monoamines be soluble in both the viscose and the baths containing zinc. The amounts to be used are smaller than 4 millimols per 100 g. of viscose.

It has proved very difiicult for these processes to be employed practically on a large scale, however, since both the amine additives and the spinning bath concentration have to be very accurately maintained in order effectively to produce the required technical result.

According to the present invention, it has now been discovered that it is possible to proceed in a much more simple manner and at the same time produce threads with even better elastic properties and higher strength values if to the viscose are added small amounts of ammonium sulphide and this viscose is thereafter spun in a weakly acid bath with a zinc sulphate content of at least 30 g./l. The amount of ammonium sulphide thus added may be up to 5% by weight, but advantageously it is in the region of 0.53% by weight.

The composition of the viscose should have an alkali/ cellulose ratio of less than 1, and preferably 0.5-0.8. It is expedient to use unripe viscoses, for example, those with a gamma value of 40 and higher.

The spinning baths preferably contain 40-65 g./l. sulphuric acid, 160-260 g./l. sodium sulphate, and more than 30 g./l. zinc sulphate, and have a temperature of 5070 C.

When using a bath zone of at least 30 cm., it is possible to openate with a withdrawal speed of 40-60 m./min. The

Y withdrawal speed may be further increased if use is made or known means to impart to the spinning bath, at least in the first pan: of its travel after the spinning nozzle, a speed which is substantially equal to the speed of the thread, so that the friction between the thread and the spinning bath is thereby substantially reduced.

In a second hot bath containing about 2-10 g./l. sulphuric acid, the threads are stretched by -120%, preferably -100%. They then show strength values of 390 g./ den., which may be increased to 420 g./ 100 den. by a final stretching operation.

In order to indicate still more fully the nature of the present invention, the following example of typical procedure is set forth, it being understood that this description is presented by way of illustration only, and not as limiting the scope of the invention.

Example 1 A viscose with the composition 8.5% of cellulose, 5.9% of NaOH and 38% of CS (prepared from high-quality cellulose) has added thereto 0.9% of ammonium sulphide (calculated on the viscose). The viscose is spun with a gamma number of 42 in a bath having the following composition: 65 g./l. H 80 235 g./l. Na SO and 50 g./l. ZnSO The bath has a temperature of 55 C. and a length of 40 cm. The Withdrawal speed used during the operation is 45 m./min. The threads are thereafter stretched by 80% in a second bath, which contains 10 g./l. H 50 and has a temperature of 90 C. The thread has a strength of 400 g./ 100 den., with an elongation of 15%; its degree of swelling is about 72%.

While a specific example of a preferred method and product embodying the present invention has been described above, it will be apparent that many changes and modifications may be made in the methods of procedure and the products without departing from the spirit of the invention. It will therefore be understood that the example cited and the methods and procedures set forth above are intended to be illustrative only and are not intended to limit the invention.

What is claimed is:

A process for the production of regenerated cellulose threads from viscose, comprising incorporating into viscose 05-50% by weight based on the viscose of ammonium sulphide, extruding the mixture into an aqueous bath containing more than 30 g./l. of zinc sulphate and 40-65 g./l. sulphuric acid, and treating the resulting extruded object in a second hot bath containing dilute sulphuric acid and stretching same by a factor of 80-120%.

References Cited in the file of this patent UNITED STATES PATENTS 2,077,412 Herzog Apr. 20, 1937 2,284,028 Ubbelohde May 26, 1942 2,506,249 Tammen May 2, 1950 2,516,316 Hare July 25, 1950 2,535,044 Cox Dec. 26, 1950 2,593,466 MacLaurin Apr. 22, 1952 2,648,611 Richter Aug. 11, 1953 2,705,184 Drisch Mar. 29, 1955 2,732,279 Tachikawa Jan. 24, 1956 2,772,444 Burrows Dec. 4, 1956 2,796,319 Studer June 18, 1957 2,884,332 Locher Apr. 8, 1959 2,892,729 Howsmon June 30, 1959 

